Schools Chancellor Joel Klein has banned the practice of putting recently retired administrators back on the payroll as pricey consultants – otherwise known as “double dipping,” The Post has learned.

Klein’s office sent a memo to all superintendents and directors saying they are forbidden from rehiring any of the more than 300 managerial employees who retired last summer.

“Individuals who took the early-retirement incentive can’t be hired as an employee or consultant,” said Department of Education spokesman Kevin Ortiz.

Klein’s office last month vetoed the renewal of a no-bid, $165,000 consulting contract for Joseph Kovaly, a retired Bronx school superintendent who last year advised school administrators on budgeting and personnel issues.

Kovaly continued to draw his pension under the original contract, which had been initiated by former Schools Chancellor Harold Levy.

State law bars retired government employees from earning a salary of more than $20,000 in the public sector while collecting a pension – unless they get a waiver, which is given only in limited circumstances. Anyone who busts the cap forfeits a portion of his pension.

But a loophole in the law treats a retired consultant as a private contractor who is exempt from the double-dipping law.

Rumors were rampant last summer that several longtime administrators who just retired – among them former personnel director Howard Tames – would reappear as consultants.

Ortiz said that’s not happening under Klein’s directive.

He said the order was put in effect to help control spending while the city grapples with a budget crunch.

The city school system has been paying out hundreds of millions of dollars on private contractors. It spends some $200 million just on “professional development” training for teachers and administrators, and millions more on computer and legal consultants.

Klein’s order doesn’t mean he’s anti-consultant. In fact, he’s brought in a team of consultants to help implement his “Children First” initiative to reform and improve the school system. But the chancellor stressed he’s using $3 million in private grants – not taxpayer dollars – to pay those consultants.